OBJECTIVE: To know how nurses working in primary care, more specifically in the Family Health Strategy (FHS), perceive their preparation for assisting the person with mental disorders and his family, and to identify the activities developed by them. METHODS: A qualitative study was conducted with 17 nurses of the ESF belonging to 21 Basic Health Units in the municipality of Maringá-PR (Brazil). Data were analyzed using content analysis methodology. RESULTS: For analysis, two categories were established: "Preparation of nurses for the development of care" and "Activities performed by nurses with families. CONCLUSION: The nurses, for the most part, did not feel prepared / qualified to attend to the specific needs of patients in the area of mental health, and their activities were restricted to those already recommended by the service, not being prepared for health promotion activities that included the family of patients with mental disorders in the care.